What does 'cook off' refer to in firearms?

The term 'cook off' in firearms specifically refers to the ignition of propellant without the striking of the primer, typically due to the heat generated in the firearm. This can occur when a heated cartridge is left in the chamber for too long, causing the propellant within the cartridge to ignite from the high temperature rather than from a firing pin strike. This phenomenon is particularly relevant in machine guns and automatic firearms, where sustained fire can lead to excess heat buildup, increasing the risk of an unintended discharge. Understanding this concept is crucial for handling firearms safely, as it highlights the importance of managing heat buildup and being aware of the operational limits of the weapon.